Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Mechanical and Aerospace Engineering

Committee Chair(s)

Stephen A. Whitmore


Stephen A. Whitmore


David Geller


Geordie Richards


A hybrid rocket is a propulsion system that uses propellants in two different phases, typically a solid fuel inside the combustion chamber and a separate gaseous or liquid oxidizer stored in a tank. Hybrid rockets are an area of research interest because of their low explosive risk, inexpensive components, and high degree of reliability. In the Propulsion Research Laboratory at Utah State University, pure oxygen is among the top choice for hybrid rocket oxidizers due to its low cost and ease of storage. When paired with a solid fuel known as ABS (acrylonitrile butadiene styrene) plastic, specific impulse values exceed 200 seconds at one atmosphere. This metric outperforms hydrazine, which is a propellant standard for in-space propulsion that exhibits high vapor toxicity and explosive hazards. However, due to the low density of oxygen, propulsion applications require storage pressures up to 3000 psig. At this high pressure, the use of oxygen can present a fire hazard. As a result, this thesis investigates the feasibility of replacing oxygen with a moderately enriched compressed air containing oxygen levels up to 40%, while maintaining performance metrics equal to or above hydrazine. To demonstrate the performance of moderately enriched air as a hybrid rocket oxidizer, comparisons to tests using pure oxygen are presented.